This is an investigation of the effects of chronic malnutrition on the social, cognitive and affective development of children. The research encompasses two parallel studies, one in Guatemala, the other in San Diego, California. Six to 10-year-old children identified as having had a history of malnutrition will be compared with non-malnourished peers on measures of functional competence. The identification of children on level of nutritional status will be based on previous nutritional history and present health and anthropometry. Behavioral assessments are made in individual and small group settings. Measures include (a) sensorimotor-cognitive variables: attentional properties, sensorimotor impulse control, reasoning and problem-solving; (b) social-emotional variables: motivational characteristics (persistence, exploration), work efficiency, moods and emotional responses, processing of social cues; and (c) social interaction variables: degree of involvement, positive and negative initiations, relationships established, emotional qualities of social exchanges.